A level shifter is used to convert an input logic voltage from a first power domain to a second power domain. In some cases, the first power domain has logic voltage levels that are smaller than the logic voltage levels of the second power domain. Likewise, the power supply or voltage supply of the first power domain is lower than the power supply or voltage supply of the second power domain. In other cases, the first power domain has logic voltage levels that are greater than the logic voltage levels of the second power domain. Likewise, the power supply or voltage supply of the first power domain is higher than the power supply or voltage supply of the second power domain in such a case.
Level shifters are widely used in today's semiconductor circuits. Level shifters are particularly useful in complex semiconductor designs, such as system on a chip (SoC), where signals are often routed through multiple power domains across the chip. Level shifters are used extensively to transition signals from one power domain to another power domain. At the same time, the requirement on the performance of level shifters has also been raised due to more stringent signal integrity requirement in low power circuits and the push for faster speed. The ability to maintain signal integrity, especially on clock signals, across wide range of input-output voltage is crucial in today's low-power high-speed mobile chips. Conventional level shifters that are susceptible to duty cycle distortion cannot meet the requirement of many low-power high-speed applications.
Accordingly, there is a need in the art for level shifters with minimal duty cycle distortion across a wide range of input-output voltage.